Search

CoZn layered double hydroxide (LDH) or Co(OH)2 pseudocapacitive material has been prepared on the current collector of carbon fiber paper (CFP) using an eco-friendly one-step electrodeposition. Benefiting from its unique structural feature, the binder-free CoZn LDH/CFP electrode material realizes high specific capacitance of 1156 Fg−1 at a current density of 1 Ag−1 and excellent rate capability of 80% retention with 16 fold current density increment, which is much better than that of Co(OH)2 (617 Fg−1, 65%). Notably, the CoZn LDH/CFP can retain an outstanding electrochemical stability with a capacitance degradation of only 6% after 6000 charge–discharge cycles at 32 Ag−1. Moreover, an asymmetric supercapacitor (ASC) using CoZn LDH/CFP as a positive electrode and AC/CFP as a negative electrode has been assembled. The ASC exhibits a superior energy density of 30.0 Whkg−1 at a power density of 800 Wkg−1 with a specific capacitance up to 84.4 Fg−1 and a potential window wide to 1.6 V. These encouraging results indicate that CoZn LDH/CFP composite material has a great potential for next-generation energy conversion/storage devices.

Lithium ion batteries are attracting ever increasing attention due to their advantages of high energy/ power density, environmental friendly, lifetime and low cost. As a star in the field of materials and energy, perovskites have received extensive attention due to their attracting physical and chemical properties. Herein, CaMnO3, one material from the perovskite family is introduced as a novel anode material for lithium ion batteries, and its electrochemical performance at different temperatures is systematically investigated. CaMnO3 has been synthesized using a liquid phase synthesis method followed by high temperature calcination. The as-obtained CaMnO3 exhibits an initial high discharge capacity of 708.4 mAh g−1, superior rate capability and stable cycling performance at room temperature, the specific capacity is 102.5 mAh g−1 after 500 cycles at a current density of 0.1 A g−1. Additionally, at an extreme temperature of 0 °C, the discapacity can reach 138.2 mAh g−1 at a current density of 0.05 A g−1. At high temperature of 50 °C, the reversible discharge capacity is up to 216.5 mAh g−1under the same condition. It is believed that this contribution may lay the foundation for the application of perovskites in other rechargeable batteries and energy storage devices.

As a new type of capacitor-battery hybrid energy storage device, metal-ion capacitors have attracted widespread attention because of their high-power density while ensuring energy density and long lifespan. Potassium-ion capacitors (KICs) featuring the merits of abundant potassium resources, lower standard electrode potential, and low cost have been considered as potential alternatives to lithium-/sodium-ion capacitors. However, KICs still face issues including unsatisfactory reaction kinetics, low energy density, and poor lifetime owing to the large radius of the potassium ion. In this Review, the importance of emerging potassium-ion capacitor is addressed. The Review offers a brief discussion of the fundamental working principle of KICs, along with an overview of recent advances and achievements of a variety of electrode materials for dual carbon and non-dual carbon KICs. Furthermore, electrolyte chemistry, binders as well as electrode/electrolyte interface, are summarized. Finally, existing challenges and perspectives on further development of KICs are also presented.

Transition metal oxides show great potential as electrocatalysts, owing to the low cost and rich chemical states. However, the limited surface areas, low intrinsic activity and poor hydrogen evolution reaction (HER) activity greatly restrict the application for overall water splitting. Herein, we have constructed S doped NiCo2O4 nanosheet arrays by Ar plasma (Ar-NiCo2O4|S) to enhance active sites and boost catalytic kinetics. Consequently, the Ar-NiCo2O4|S shows the improved performances for HER and oxygen evolution reaction (OER). Further, as bifunctional electrocatalysts, Ar-NiCo2O4|S exhibit a voltage of 1.63 V at 10 mA cm−2, as well as good stability.

Cost effective anode material with rational design is of significance for rechargeable potassium ion batteries (KIBs). Graphite anode currently still suffers unfavorable rate capability and moderate cycling stability. In this work, we report a mesoporous carbon sphere with rich porous structure as an anode material for KIBs with the assistance of an aerosol spray technology. The as-developed carbon spheres exhibit a well-defined spherical structure with favorable surface area of 1106.32 m2 g−1. Furthermore, the effect of different electrolytes on the electrochemical performance of the carbon anode has been investigated systematically. As expected, the carbon material shows excellent potassium storage performance in terms of improved specific capacity of 188.2 mAh g−1, rate capability and prolonged cyclability with a high capacity of 105.3 mAh g−1 after 500 cycles at a rate of 100 mA g−1 toward potassium storage in KFSI based carbonate electrolyte.

Hybrid ion capacitors show promise to bridge the gap between rechargeable batteries with high energy density and supercapacitors of high power. However, research efforts primarily focus on lithium-ion and/or sodium-ion based capacitors, potassium ion capacitor (KIC) is theoretically more sustainable and promising owing to the high abundance, low standard redox potential and low cost of the K sources. Herein, nitrogen-doped porous carbon submicrospheres derived from hierarchical micro-flowerlike polyimide superstructure are fabricated and investigated as novel anodes for excellent K ion storage. The effect of different electrolytes on potassium storage properties and the reaction kinetics are successfully revealed. A low cost nonaqueous KIC is assembled with commercial activated carbon as cathode and the polyimide derived carbon as anode. Benefiting from the unique structure characteristics of enriched active sites, high electronic conductivity, and the conspicuous pseudocapacitive effect of polyimide carbon, the as-fabricated device manifests the maximum energy density and power density of 90.1 Wh kg−1 and 3000 W kg−1, respectively. Even at 1540 W kg−1, the energy density still remains at 43.5 Wh kg−1. Moreover, the device achieves a near 100% Coulombic efficiency and favorable cycling stability over 5000 cycles at a current density 500 mA g−1.